As one of the methods for preparing (meth)acryl group-containing organosiloxanes, there is known the method of conducting a hydrosilylation reaction between SiH group-containing organopolysiloxanes and alkenyl group-containing (meth)acrylic compounds in the presence of a platinum catalyst (as disclosed in Japan Tokkai No. 48-47998). Herein, the term "Japan Tokkai" stands for an unexamined published Japanese patent application.
However, the above-cited method has a problem wherein the yield rate of the intended (meth)acryl group-containing organosiloxane is markedly reduced due to the condition that part of the SiH groups can react on the (meth)acryl groups, apart from the case in which the SiH groups selectively react only on the alkenyl group contained in a (meth) acrylic compound to effect hydrosilylation.
The problem of reaction selectivity in the above-described hydrosilylation can be solved by adopting the method of first causing (meth)acrylic acid to react on an epoxy group-containing siloxane and then causing (meth)acrylic acid chloride to react on the thus obtained product in the presence of a hydrogen chloride scavenger (as disclosed in Japan Tokkai No. 63-135426).
In such a method, however, it is necessary to prepare in advance the epoxy group-containing siloxane by conducting the hydrosilylation reaction between the SiH group-containing siloxane and the alkenyl group-containing epoxy compound in the presence of a platinum catalyst. This method also, therefore, has a disadvantage in that the preparation requires several reaction steps.
Further, there is known another method in which the alkoxy group(s) of a (meth)acryloxy group-containing alkoxysilane is(are) hydrolyzed using a highly nucleophilic acid as catalyst.
The above-cited method, however, is accompanied by a side-reaction such that the (meth)acrylate moiety is also hydrolyzed. Therefore, it suffers from a defect that the by-products arising from the side-reaction exert bad influences upon the reactivity of the intended compound in the next reaction step and upon physical properties of the final product obtained therefrom.